Out of the Bassian province: historical biogeography of the Australasian platycercine parrots (Aves, Psittaciformes) MANUEL SCHWEIZER,MARCEL GU ¨ NTERT &STEFAN T. HERTWIG Submitted: 6 March 2012 Accepted: 2 July 2012 doi:10.1111/j.1463-6409.2012.00561.x Schweizer, M., Gu ¨ ntert, M. & Hertwig, S. T. (2012). Out of the Bassian province: histori- cal biogeography of the Australasian platycercine parrots (Aves, Psittaciformes). —Zoologica Scripta, 00, 000–000. Aridification from mid-Miocene onwards led to a fragmentation of mesic biomes in Aus- tralia and an expansion of arid habitats. This influenced the diversification of terrestrial organisms, and the general direction of their radiations is supposed to have been from mesic into drier habitats. We tested this hypothesis in the platycercine parrots that occur in different habitats in Australia and also colonized Pacific islands. We inferred their tem- poral and spatial diversification patterns using a Bayesian relaxed molecular clock approach based on three nuclear and two mitochondrial genes and model-based biogeographic reconstructions. The Bassian biota was found to be the centre of origin of platycercine parrots and diversification within two of their three clades coincided with the beginning of aridification of Australia. The associated habitat changes may have catalysed their radiation through adaptation to arid environments and vicariance because of the fragmentation of non-arid habitats. The small oceanic islands of Melanesia contributed as stepping stones for the colonization of New Zealand from Australia. Corresponding author: Manuel Schweizer, Naturhistorisches Museum der Burgergemeinde Bern, Bernastrasse 15, CH 3005 Bern, Switzerland. E-mail: manuel.schweizer@nmbe.ch Stefan T. Hertwig and Marcel Gu ¨ ntert, Naturhistorisches Museum der Burgergemeinde Bern, Bernastrasse 15, CH 3005 Bern, Switzerland. E-mails: stefan.hertwig@nmbe.ch, marcel.guentert@ nmbe.ch High Taxon Name: Aves, Psittaciformes, Platycercinae No new taxa described. Introduction The avifauna of the Australasian region and especially of its oceanic islands has played an important role for the development of theories on speciation and biogeography as well as the evolution of continental biota (Cracraft 1986; Filardi & Moyle 2005; Mayr & Diamond 2001; McDowall 2008; Wallace 1867). The core of the Austral- asian bird fauna has a Gondwana origin and has radiated in isolation during the Palaeogene under the influence of climate and environmental change as well as tectonic activ- ities (Schodde 2006; Christidis & Norman 2010; Trewick & Gibb 2010). The aridification of the Australian conti- nent beginning in the middle Miocene or perhaps even earlier seems to have had a major influence on the diversi- fication of the Australian bird fauna (Schodde 2006; Byrne et al. 2011). Then, a major change of vegetation began in Australia with shrinkage of rainforests, fragmentation of mesic biomes and an expansion of drier, more open sclero- phyll forests. Today, arid and semi-arid habitats cover much of the Australian continent (Jacobs et al. 1999; Martin 2006; Schodde 2006). The general direction of radiation for land birds and other taxonomic groups in Australasia has been suggested to be from rainforests into drier and more open habitats (Schodde 2006; Byrne et al. 2008, 2011). Ancestors of recent arid taxa may have either diverged from their closest relatives before the onset of aridification and adapted to arid environment in situ or originated from mesic ancestors through multiple diversifi- cation and colonization events of arid regions (reviewed in Byrne et al. 2008). The fragmentation of mesic biomes moreover led to localized endemism and phylogeographic structure in taxa specialized on these habitats (cf. e.g. Schodde 2006; Byrne et al. 2011). Parrots are one of the dominant elements of the Eyrean avifauna of the arid parts of Australia (Schodde 2006), and especially, members of the cockatoos and of the broad- tailed or platycercine parrots (Platycercinae, consisting of Pezoporini and Platycercini, Joseph et al. (2012)) are today ª 2012 The Authors d Zoologica Scripta ª 2012 The Norwegian Academy of Science and Letters 1 Zoologica Scripta